There are different processes for making α,β-unsaturated cyclic imidoalkoxysilanes that are known in the art. These processes are based on the condensation of anhydride precursors with primary aminoalkoxysilanes, and produce water as one of the reaction by-products. Typically, the water produced is scavenged from the reaction using one or more chemical desiccants, for example hexamethyldisilazane (HMDZ) or trimethylsilyl chloride (TMSCI). These chemical desiccants must be used in at least stoichiometeric amounts, which makes these processes economically unfeasible when used to produce α,β-unsaturated cyclic imidoalkoxysilanes on a large commercial scale.
One object of the invention is directed to a process for producing α,β-unsaturated cyclic imidoalkoxysilanes under conditions favorable to allow the removal of water produced by reaction using azeotropic distillation instead of chemical desiccants. In particular this object of the invention is directed to a process for making α,β-unsaturated cyclic imidoalkoxysilanes using a Diels-Alder protection strategy without using chemical desiccants.
Another object of the invention is directed to stable Diels-Alder intermediates that can be used to produce α,β-unsaturated cyclic imidoalkoxysilanes of the present invention.
Still another object of the invention is directed to the process for producing a Diels-Alder unsaturated N-substituted aromatic imide using an aromatic primary amine and an anhydride precursor in a solvent that permits the removal of water using azeotropic distillation instead of a chemical desiccant.
The objects of the present invention overcome the shortcomings of the known processes and are further described below.